New Zealand took a firm grip on this year's Tri-Nations with a 31-17 victory over South Africa in their clash at the Westpac Stadium in Wellington.

Tries from centre Ma'a Nonu, fullback Mils Muliaina, wing Rene Ranger and a superb solo effort from replacement Israel Dagg ensured the All Blacks secured back-to-back bonus point wins at the expense of their old rivals.

The Springboks were again left to rue some costly indiscipline that saw Danie Rossouw yellow-carded early in the first half but the lock bounced back to notch a try just before the break. Flanker Schalk Burger also crossed for the visitors but it was no more than a consolation score with the All Blacks having dominated proceedings thanks to a fast-paced and clinical showing.

New Zealand made two changes to the side that eclipsed the Boks 32-12 in Auckland last weekend with Piri Weepu getting the nod over Jimmy Cowan at scrum-half while Ranger was handed his first start in the place of the injured Joe Rokocoko. South Africa kept faith with the majority of the side outclassed at Eden Park with Rossouw promoted in the place of the suspended Bakkies Botha while CJ van der Linde started at tight-head following an injury to Jannie du Plessis.

The Springboks weathered an early storm before being handed the chance to open the scores when All Blacks No.8 Kieran Read was penalised at the breakdown. But the visitors' hopes of stealing the initiative were dealt a blow by referee Alain Rolland who reversed the penalty after Rossouw appeared to lash out at All Blacks captain Richie McCaw. The replay appeared to suggest he had been harshly treated but that was little consolation for the lock who was also sent to the sin-bin on the occasion of his 50th Test appearance.

The All Blacks looked to capitalise immediately although Carter was wayward with a penalty the hosts were soon knocking on the door again with quick ball stretching the Boks before Nonu showed great strength to power over for the game's first try.

The All Blacks' impressive pace and intensity brought further reward with turnover ball in midfield snaffled by scrum-half Piri Weepu who surged through the Springboks' line before feeding Muliaina who had the pace to power towards the corner for his side's second try. Carter's off-day with the boot continued in the wind and rain with his third kick of the night failing to find its target.

The Springboks continued to get very little change out of a fired-up All Blacks defence and opted for a return to the aerial route that brought them little joy at Auckland last weekend. And it was a similar story this time around with the Springboks looking alarmingly short of attacking ideas.

Unsurprisingly it was the All Blacks who were next to trouble the scoreboard with Carter rediscovering his touch with a penalty that took his side out to a 13-0 lead. With the half coming to a close, a big hit from All Blacks winger Rene Ranger on Springboks fullback Zane Kirchner drew a word of warning from Rolland and allowed the visitors to take the game into the New Zealand 22. Scrum-half Ricky Januarie and wing Jean de Villiers made big gains off the resulting lineout and Rossouw capped a rollercoaster of a half by driving over for a try under the posts that was converted by Steyn.

New Zealand had the chance to have the final say in an intriguing first half when South Africa's indiscipline cost them once again a the breakdown but Carter was unable to punish them further.

Wing Gio Aplon and prop BJ Botha entered the fray for the Springboks after the break and as in Auckland they raised their game after the interval to good effect with McCaw penalised for his desperate attempts to snuff out an attack in the shadow of his own posts. And Steyn reduced the arrears with the subsequent kick.

The All Blacks responded in the only way they know how with a well-worked try for Ranger. Muliaina made the initial incision and the veteran was the link man again after some good work from Carter, eventually feeding Ranger out wide. The winger then showed great awareness to lift his feet off the ground in the process of scoring to deny Aplon a try-saving tackle. In a rare switch, Weepu was handed the kicking duties when another penalty came the All Blacks' way moments later and he produced a great kick on his home ground to extend his side's lead.

Andries Bekker and Ruan Pienaar were introduced by the Springboks in an attempt to stop the rot and the changes brought a renewed effort from the visitors but slow ball and handling errors were their undoing. But they were soon knocking on the door again with the dancing feet of Aplon going close with McCaw eventually getting a final warning from Rolland as the All Blacks desperately re-grouped.

The All Blacks' physicality continued to frustrate the Springboks and that workload soon saw the introduction of Cowan, Tom Donnelly and Dagg with the latter making an immediate impression with a superb try. The youngster displayed incredible pace and skill to dance through the Springboks defence leaving Pierre Spies and Schalk Burger in his wake before dotting down in the corner to ensure the bonus point. Carter nailed the conversion from outwide to put his side on course for victory.

The score did little to diminish the All Blacks' hunger and high tackle from Kirchner on wing Cory Jane allowed Carter to heap more woe on the Springboks who introduced Ryan Kankowski for Spies with ten minutes of the game remaining. Aaron Cruden was also handed a chance to impress in the place of Nonu but he could do little to stop Burger barging his way over as the otherwise resolute All Blacks' defence finally began to show signs of fatigue. Steyn added the extras as his captain John Smit made way for Chiliboy Ralepelle while McCaw was also withdrawn amongst changes that saw Liam Messam and Corey Flynn join the action.

The Springboks battled valiantly until the final whistle but for the second week running they came up empty-handed against a superior All Blacks side that remain in pole position for this year's title.